/* --------------------------------------------------------------------------
CppAD: C++ Algorithmic Differentiation: Copyright (C) 2003-17 Bradley M. Bell

CppAD is distributed under multiple licenses. This distribution is under
the terms of the
                    Eclipse Public License Version 1.0.

A copy of this license is included in the COPYING file of this distribution.
Please visit http://www.coin-or.org/CppAD/ for information on other licenses.
-------------------------------------------------------------------------- */
/*
$begin exp_2_rev2.cpp$$
$spell
	cstddef
	cmath
	exp_2_rev
	bool
	std
	fabs
$$

$section exp_2: Verify Second Order Reverse Sweep$$
$mindex exp_2 mode$$



$srccode%cpp% */
# include <cstddef>                 // define size_t
# include <cmath>                   // prototype for fabs
extern bool exp_2_for0(double *v0); // computes zero order forward sweep
extern bool exp_2_for1(double *v1); // computes first order forward sweep
bool exp_2_rev2(void)
{	bool ok = true;

	// set the value of v0[j], v1[j] for j = 1 , ... , 5
	double v0[6], v1[6];
	ok &= exp_2_for0(v0);
	ok &= exp_2_for1(v1);

	// initial all partial derivatives as zero
	double f_v0[6], f_v1[6];
	size_t j;
	for(j = 0; j < 6; j++)
	{	f_v0[j] = 0.;
		f_v1[j] = 0.;
	}

	// set partial derivative for f_5
	f_v1[5] = 1.;
	ok &= std::fabs( f_v1[5] - 1. ) <= 1e-10; // partial f_5 w.r.t v_5^1

	// f_4 = f_5( v_1^0 , ... , v_4^1 , v_2^0 + v_4^0 , v_2^1 + v_4^1 )
	f_v0[2] += f_v0[5] * 1.;
	f_v0[4] += f_v0[5] * 1.;
	f_v1[2] += f_v1[5] * 1.;
	f_v1[4] += f_v1[5] * 1.;
	ok &= std::fabs( f_v0[2] - 0. ) <= 1e-10; // partial f_4 w.r.t. v_2^0
	ok &= std::fabs( f_v0[4] - 0. ) <= 1e-10; // partial f_4 w.r.t. v_4^0
	ok &= std::fabs( f_v1[2] - 1. ) <= 1e-10; // partial f_4 w.r.t. v_2^1
	ok &= std::fabs( f_v1[4] - 1. ) <= 1e-10; // partial f_4 w.r.t. v_4^1

	// f_3 = f_4( v_1^0 , ... , v_3^1, v_3^0 / 2 , v_3^1 / 2 )
	f_v0[3] += f_v0[4] / 2.;
	f_v1[3] += f_v1[4] / 2.;
	ok &= std::fabs( f_v0[3] - 0.  ) <= 1e-10; // partial f_3 w.r.t. v_3^0
	ok &= std::fabs( f_v1[3] - 0.5 ) <= 1e-10; // partial f_3 w.r.t. v_3^1

	// f_2 = f_3(  v_1^0 , ... , v_2^1, v_1^0 * v_1^0 , 2 * v_1^0 * v_1^1 )
	f_v0[1] += f_v0[3] * 2. * v0[1];
	f_v0[1] += f_v1[3] * 2. * v1[1];
	f_v1[1] += f_v1[3] * 2. * v0[1];
	ok &= std::fabs( f_v0[1] - 1.  ) <= 1e-10; // partial f_2 w.r.t. v_1^0
	ok &= std::fabs( f_v1[1] - 0.5 ) <= 1e-10; // partial f_2 w.r.t. v_1^1

	// f_1 = f_2( v_1^0 , v_1^1 , 1 + v_1^0 , v_1^1 )
	f_v0[1] += f_v0[2] * 1.;
	f_v1[1] += f_v1[2] * 1.;
	ok &= std::fabs( f_v0[1] - 1. ) <= 1e-10; // partial f_1 w.r.t. v_1^0
	ok &= std::fabs( f_v1[1] - 1.5) <= 1e-10; // partial f_1 w.r.t. v_1^1

	return ok;
}
/* %$$
$end
*/
